Expansion bit



J. W. JACOBS Feb. 2, 1960 EXPANSION BIT 2 Sheets-Sheet 1 Filed Jan. 30,1956 IN V EN TOR. 7 M

FIG

JOHN w. JACOBS FIG FIG

fu I... I ll\ 1950 J. w. JACOBS 2,923,336

EXPANSION BIT Filed Jan. 30, 1956 2 Sheets-Sheet 2 FIG 54 (h. .1

JOHN W. JACOBS INVENTOR.

United States Pa t EXPANSION BIT John W. Jacobs, Seattle, Wash.Application January 30, 1956, Serial No. 562,085

2 Claims. or. 145-127 This present invention relates to the general artof wood boring bits and more particularly to an expansion bit. Thisdesign is further characterized by means which greatly facilitate theaccurate expanding or retraction of the movable cutters and when theyare properly positioned and their diametrical distance has beenadequately checked, means are provided for adequately locking theactuating-mechanism so that the entire assembly is definitely lockedagainst any change of adjustments.

Expansion bits have been employed by carpenters and others working inwood for many years and-many different styles have been produced. Thispresent invention follows certain of the principles formerly employed,namely that in the preferred form two opposed cutters are employed whichare adjustable along their longitudinal axis so that a wide range ofhole sizes can be bored with the device. In the past a most common faultwith extension bits has been the inability to provide adequate adjustingand securing means. A- common form has been merely to have the cutterslongitudinally adjustable in metal recesses or slots and then to havesome form of a locking screw to bind them in the adjusted position. Someattempts have been made further to employrack gears cut on the cuttersthemselves and with a spur gear pinion adapted to engage the same eitheras a component of the bit or as a unit temporarily applied to theadjustment of the cutters. Such means have a common fault with thesimpler forms in that there is no definite locking of the bit in itsextended position.

In my present expansion bit I employ teeth cut on the upper edge of thecutter bars but form these teeth with adequate clearance so that theactuating means which is a worm or screw thread will engage the teeth ina manner so that there is no end or longitudinal movement possible inthe cutter bars. This arrangement is ineffect a singlethread wormgear'of which parts have been cut away in formingthe' operational partsof'this device. The outstanding characteristic of the single threadworm, namely that it is self-locking, is however retained in'thisconstruction so that'any tendency for the cutter to crowd away from hardspots, in either direction, from its adjusted position is met by theWorm which holds it against movement. Further, the locking of the cutterbar rack-by the spiral thread arrangement provides such a small angle offorce application that there is .no possibility of pressure on thecutter tooth actually turning the actuating and positioning =worm orthreaded nut. It follows therefore that when the bit is adjusted it isonly necessary to provide some form of functional lock for the screwthread nut in order to insure that it is not moved as might occur inlaying the tool down or something of that order. In otherwords the finallocking means merely secures the actuating worm against movement and inthis way a very secure locking of the tool is provided. v

in thezpast carpenters have been greatly inconvenienced :by-rthefactthat once they would Start alarge hole, for

2,923,336 I Fiatented Feb. 2, 1aso lice instance in a door for theinstallation of af lock, they had little if anyway of having anindication of any change in the cutting diameter of the bit .until itemerged froi'n the opposite side-of the door. There are few carpentersthat have not had the experience of actually spoiling doors and. likefinished work parts by having the bit change its cutting diameter andthus in many cases provide an exit opening of largerdiameter which inmany cases could notbe coveredby the fittings of the lock or thediameter would be reduced so a conical hole was produced and this wouldrequire reworking as withrasps and the like in order that the lock couldbe fitted. All these faults are either annoyingv or destroy expensiveparts or consume a great dealof time which in turn ,is quite valuable onthe present labor market. In my present expansion. bit it. is believedthat a great many of the outstanding. deficiencies of the present formsof expansion bits have been overcome and a bit provided that will insurethe most ex-acting'work' with the minimum of ex penditure of time. I

The principal object of this invention therefor is to provide anexpansion bit thatis easily adjusted to exact dimension andwhen onceadjusted can be securely locked in its adjusted position, I

A further object of this present invention is to pro vide a positioningand securing'meansifor an extendable cutting blade which makes use ofthe self-locking prinf ciples of a single thread worm to the end thatsecure lockingof the device can be depended upon;

A further object of this. present invention is to provide locking meansfor. extendablecutter bits in an extensiontool in which the mainpositioning and locking means is further provided .with a secondary lockto the 'end that the device can be. dependedupon to maintain thisextended position throughout an entire operation,

A further object ofthisip'resent invention is to provide an expansiblebit employing two Qopposedcutters to the'en'd that the-cutting circlecan belaccurately measured and set in the desired position.

Further objects, advantages and capabilities will be apparent from thedescription and disclosurein the draw% ings, or may be comprehended orare inherent. inthe device.

Figure 1 is a perspective view showing a preferred form of my presentinvention with certain parts being shown in section. I v I Figure 2 is aside elevation, partly in section, of the form of my tool as illustratedin Figure l. v

. Figure 3 is anelevational viewtaken as though the device of Figure 2were revolved 9.0,degrees and with certain parts shown insection andinda'shed lines to better illustrate the construction. The irregularcutting plane is substantially through the center of the device ofFigure 2. 3

Figure 4 is an elevation view,,partly in section, illustrating amodified form of thy-device in whichor ly one cutter .is employed. f 1

Figure 5 is an elevation, pzartlyinsection, to illustrate the internalstructure, the showing being'revolved 9.0 degrees from the position ofFigure 7 v 'j Figure 6 is a perspective view, partly in section,illustrative of the cupped tensio-ning vwasher employed to asaassa withthe conventional four sided tapered end that is characteristic ofordinary wood bits and adapts the same for use in hand operatedcarpenters braces. The lower body of member 1 terminates in a lead screw14 of a type normally employed on wood bits, angers and the like.Positioned above lead screw portion'14 is a cutter member 16 and aspiral grooved portion 18. This arrangement insures that the bodyportion of my expansion bitwill have its own means of disposing of thewood in its path so that it may progress through the wood being boredand make it possible for the extendable cutters to be led into the woodwith adequate pressure to insure their biting in and boring through thepiece.

v Member 10 is slotted to accept either the two extendable cutters as 20and 22 of the preferred form of my invention or it may be slotted forthe single cutter as 24, illustrated in the modified 'form ofmy devicein Figures 4 and 5. In all the forms, cutters 20, 22 and 24 are disposedat an angle to the vertical axis substantially as illustrated in Figures3 and to the end that the initial cutter element 25 may engage the woodfirst and then the main cutting edge 27 of the cutter blade itselfsuccessively engages the wood so that the hole is outlined at the startand all cross-grained wood prevented from splitting outside the holebeing bored. This inclination of the cutters calls for similardisposition of the slots as 26 and 28 of the double or preferred formand 30 in the single cutter form. These slots provide a snug butworkable engagement of the cutters on both sides aswell as the edgeswhich are actually more critical. The portion between shank 12 and theenlarged portion in which the various slots occur is preferably threadedas at 32 with a relatively fine thread so that the locking nut member 34or 54 can be securely seated. Because of the relatively flat pitch whichis a function of the fine threads there will be little tendency for thenut to loosen and this can be met by providing a bar washer, bent on asingle axis, as 36, which will at all times, keep the nut tight againstthe threaded portion 32. The enlarged portion of the auger member 10 isprovided with a ledge-like seat as 38 and is provided with a bore as 40of reduced diameter so that the worm'or spiral threaded ring 42 will becentered and positioned in its operational relationship with the cuttermembers as 20, 22, and 24. Annular engaging member 42 is preferablycounter-bored so as to accept a reduced diameter portion of the lock nut34 or 54. This relationship is quite well illustrated in Figures 3 and 5of the drawings. The outer surfaces of member 42 and nut 34 arepreferably knurled so that hand manipulation of these members will befacilitated. It is to be noted that in the operation of my device thathand operation is all that is required for the security of the elementsin their locked or adjusted positions, it not being necessary to employwrenches as are so often used with other types of this equipment.

As it will be noted in Figures 3 and 5 the lower sur-.

face of adjusting member 42 takes on the same angle with respect to thevertical axis of the device as the cutters as 20, 22 or 24 thatitengages. It is noteworthy that the inclination of the cutters makes itpossible for ringlike member 42 to engage teeth 43 of the cutter only atone point, consequently this angular relationship is easily maintainedand makes for snug engagement which in turn means accurate adjustmentthat will be readily maintainable over long periods of use. The annularengaging member 42 is provided with a spirally arranged gear tooth orgroove 44. The arrangement of these grooves however, actually producesthe tooth-like forms illustrated in Figures 3 and 5. This tooth disposedon the relatively large diameter acts in the same manner as a spiral orworm gear in that 7 formed on device 42 and the teeth 43 of the variousracks is so slight that no normal amount of pressure on the cutters canrevolve member 42 and change the adjustthe angularity between the teethment. This is a very important characteristic of this present invention.It is to be noted that the adjustment of the cutters by means of theadjusting member 42 is easily aifected with the unaided fingers and thenwhen an adjusted position has been obtained the lock-nut 34 which isprovided with a relatively fine, or so-called automobile thread 32 caneasily be seated tightly enough with the unaided fingers so that thewhole unit is a securely, locked in position, assembly. It is to benoted that in the mod ified form shown in Figures 4 and 5 this bare handsetting of the locking member has been substituted for by the lockingmember 54 which is otherwise similar but is provided with a shortenedthread area 56 and the actual turning of the lock nut is accomplished bya spanner wrench which fits the detent openings as 58 formed in the nutmember. This arrangement is intended more for use in power equipmentwhere the device might be set up for a definite size hole and left inthat adjusted position for many successive periods of use. Referring tothe preferred form shown in Figures 1, 2 and 3 it is to be noted thatcutters 20 and 22 are positioned in communicating slots 26 and 28 in abac'k-to-back arrangement; however the positioning slots 26 and 28 areoppositely pitched, after the showing of Figure 3 so that for a goodportion of their extent they are in effect sep arate slots which aremerely brought together at their mid portions in order to facilitatemachining and to bring the two cutters close together so that a morediametrical position of the opposed cutter points 25 can be achieved. Itis believed that it will be clearly apparent from the above descriptionand the disclosure in the drawings that the invention comprehends anovel construction of an expansion wood bit.

Having thus disclosed the invention, I claim: 4

1. An expansion wood bit, comprising: a central auger member having anupwardly extending shank, a lower body and a bottom lead screw, saidauger body having a slot extending transversely therethrough andangularly disposed with the longitudinal axis of said auger member; anextendable cutter bar slidably mounted in said through slot, said cutterbar having a depending sharpened cutter tooth at one end and forming anobtuse angle with the longitudinal axis of said shank and having acutting edge extending from said tooth along the lower margin of oneface thereof; said cutter'bar having teeth with their faces extendingtransversely thereof and formed in a row extending along the cuttersupper surface; an-annular engaging member having an engaging face angularly disposed to make a full engagement with. the faces of said teethof the cutter bar, mounted coaxially on said auger body and manuallyoperable to engage said upper teeth of said cutter bar on one side onlyof said annular engaging member to hold the cutter bar against movementalong its longitudinal axis; said annular engaging member having toothengaging portions which are near right-angular with respect to thecutter bar longitudinal axis so that the pressure of the cutter upperteeth thereagainst will have little camming action to displace theengaging member transversely to the side; said annular engaging memberhaving spirally disposed groove means on its lower surface which formthe tooth engaging portions for the cutter bar upper teeth; said annularmember being rotatably mounted on said auger body and the spiral groovehaving sufficient inclination, relative said upper teeth faces, to movesaid cutter bar in said slot as said annular engaging member is rotated;and locking means for holding said annular member against rotarydisplacement consisting of a locking nut rotatably mounted on said augershank and having threaded connection therewith whereby the locking nutmay be tightened to press said annular'engaging member against saidcutter bar to frictionally hold the same against rotation.

2. An expansion wood bit, comprising: an auger body and a shank upwardlyextending therefrom and a bottom lead screw on said auger body, a pairof through slots extending transversely through said auger body andslanted oppositely relative the horizontal and said through slots beingjuxtaposed and being in communication in their central portions, a pairof extendable cutter bars disposed in said through slots, slanted atdifferent angles regarding each other by the inclination of said throughslots and said cutter bars having their abutting sides in contactthroughout their central portions; said cutter bars each having adepending sharpened cutter tooth at its lower outer end and having acutting edge along the lower margin of one face, said cutter bars eachhaving a series of teeth disposed along its upper edge with the toothfaces oriented transversely of the cutter bars, said auger body havingan annular locking ring rotatably mounted on its upper portion and thelocking ring having spiral groove means on its bottom disposed in aplane normal to the longitudinal axis of said auger body engaged withthe adjacent teeth of said cutter bars, the groove means on said lockingring having only slight inclination relative the faces of the cutter barteeth whereby pressures on said locking ring by said cutter bars havelittle camrning force on said ring to rotate the same, said locking ringbeing manually rotatable and moving the cutter bars an equal distanceinward and outward upon rotation thereof; a locking nut abutting theupper portion of said locking ring and said nut having a central openinghaving threaded engagement with said auger shank and said locking nutbeing rotatable to press against locking ring to frictionally hold thelocking ring against rotation.

References Cited in the file of this patent UNITED STATES PATENTS318,897 Harrison May 26, 1885 988,143 Pope Mar. 28, 1911 1,004,572Jennings Oct. 3, 1911 1,165,854 Davis Dec. 28, 1915 1,206,363 PassauerNov. 28, 1916 1,232,397 Sheets July 3, 1917 1,845,119 Benson Feb. 16,1932 FOREIGN PATENTS 423,259 Great Britain Jan. 29, 1935

